Tandberg Data
Log Sense
13-33
Tandberg SLR Product Line SCSI Functional Specifications
Remaining Capacity
Counter - Current
Partition
When the drive operates in write mode this counter
counts/presents the remaining physical native capacity
of the current (active) partition, scaled in KBytes.
When the drive operates in read mode this counter will
reflect the potential amount of data stored from the
current tape position to the end of the partition and
not the actual remaining storage capacity of the
partition.
Note that the capacity indicated is the capacity up to
the logical early warning marker.
This counter is not designed for use as an absolute
count of remaining capacity at any arbitrary moment, but
as a means to calculate the approximate fraction of tape
usage during backup or restore operations.
Any attempt by the initiator to alter this counter will
be ignored.
Notes:
The Remaining Capacity counter presents an approximate
amount of native physical data which can be written to
the current tape partition. This count can be related
to logical user data only if the tape drive is used in
an optimal way. A high number of underruns during
write (due to a tape of poor quality, not favorable
system settings, low host transfer rate and/or writing
of a small amount of data per session) or excessive
use of forced streaming might reduce the actual
remaining capacity significantly. In addition, the
counter does not reflect any impact of a possible use
of data compression. The Remaining Capacity counter is
controlled by processes on the tape of the data buffer
and is thus not fully synchronized with the data
stream on the SCSI-bus.
The Current Partition number can be obtained from the
Active Partition field of the Device Configuration
Page using a MODE SENSE command. The number of
additional partitions on the currently inserted tape
can be obtained from the Additional Partitions Defined
field of the Medium Partition Page using a MODE SENSE
command.
